Mike Pence visited Iowa this week to pitch the Trump administration’s USMCA trade deal and ask Iowans to “turn up the heat” on their Democratic representatives in Congress to pass the legislation designed to replace Nafta.

Speaking to a crowd of more than 500 supporters at Manning Farms in Waukee, a suburb of the capital, Des Moines, the vice-president had come to Iowa to push the deal, which was agreed in November 2018 between the US, Mexico and Canada but has yet to be passed by Congress.

“It’s time for Democrats in Congress to do their job, put politics aside and pass the USMCA this year,” he said. “The truth is, and we all know it, the Democrats have been spending all their time on endless investigations and a partisan impeachment. But enough is enough, the American people deserve better,” he concluded.

But the specter of impeachment nonetheless overshadowed the proceedings organized by America First Policies, a not-for-profit that seeks to advance the Trump administration’s policies.

Speaking to reporters after the event, Pence denied that the partial transcript of a 25 July conversation between Donald Trump and Ukraine’s president, Volodymyr Zelenskiy, amounted to a quid pro quo that $250m of military aid was dependent on Ukraine launching an investigation into Joe Biden’s son Hunter.

“The issue of aid and our efforts with regard to Ukraine were, from my experience, in no way connected to the very legitimate concern the American people have about corruption that took place, about things that happened in the 2016 election and … about the issue that former vice-president Biden had his son on the board of a major energy company in Ukraine at a time that vice-president Biden was running the United States efforts in Ukraine,” he said, repeating a White House line that seeks to shift the focus on to one of the Democratic frontrunners to take on Trump in the 2020 election.

Pressed further on the transcript, Pence argued that “a clear reading of the transcript shows that there was no quid pro quo in the president’s call with President Zelenskiy”.

Asked whether the White House would therefore release its own transcripts to back up their claims, Pence said: “I’d have no objection to that, we’re discussing that with White House counsel as we speak.”

Iowa plays a key role in the electoral calendar as the first state in the nation to vote in its February caucus, which ensures a steady stream of presidential candidates visit every four years. “If you run into them at a diner or a street corner, which I know is pretty common around here in Iowa,” Pence joked, “tell the Democrats running for the highest office in the land that Iowa needs the USMCA.” He stated that every Democrat running for president is currently opposed to the USMCA.

As the nation’s largest producer of corn and pork products and second largest soya bean producer, the USMCA is critically important to Iowa’s economy with Mexico and Canada, accounting for almost half of its exports.

The Iowa state senator Joni Ernst, who took the stage before Pence, described the USMCA as “a big deal for Iowa”, especially for its dairy farmers and pork producers. “Over 300 days ago President Trump signed this agreement,” she said. “Let me say that again, 300 days ago. I’d say that it’s time for the house to pass USMCA,” she repeated, laying the blame at House speaker Nancy Pelosi’s feet for Congress’s failure to pass the act.

Jerry Vanwyk, a corn, bean and cow farmer from Pella, about 50 miles east of Des Moines, admitted that Trump’s trade tariffs had affected his business, but reasoned: “We gotta do something … I’m at the stage of life where I can afford to be a long-range thinker and I’m concerned about the future of our country not what’s happening today.

“I just like the way our president is standing up for our country,” he explained. “It’s time we quit being walked over.”

“I think it’s a very good thing and I think the Democrats are stalling putting it on the floor,” said Wendi Gibson from Laurel. “Nafta was horrible for this country, anything has got to be better than Nafta,” she said, declining to go into specifics.

Attendees at the event believed the impeachment proceedings lack substance. “So far all the claims against the president have turned out to be useless so I’m just sort of waiting to see what happens,” said Sarah Anderson from Marshalltown.

“I think it’s garbage,” said Gerald Johnson from Adel. “I think it’s just one of those things that instead of focusing on the issues they’re focusing on things that are easy targets. When you look at everything that’s going on with that it’s like they’re trying to make things up to make them important – to me, it just doesn’t seem important. It’s a minor thing that happened on the phone call.”

“Witch-hunt!” argued Mark Harvey from Grimes, echoing language Trump has regularly used in his own tweets. “It will just make them stronger,” he said, referring to the Republican party.